Method of making a tobacco extract

ABSTRACT

Embodiments described herein include a method of making a tobacco extract comprising; (a) contacting tobacco with an extraction solvent such that tobacco components are extracted from the tobacco into the solvent, wherein the extraction solvent comprises a supercritical fluid; (b) separating residual tobacco solids from the extraction solvent containing tobacco components; (c) providing an entrapment solvent in a vessel, exposing the extraction solvent containing tobacco components to conditions in that vessel, wherein the conditions in the vessel are such that the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, and wherein the entrapment solvent dissolves the tobacco components released from the extraction solvent.

PRIORITY CLAIM

The present application is a National Phase entry of PCT Application No. PCT/EP2018/062121, filed May 9, 2018, which claims priority from GB Patent Application No. 1707764.5, filed May 15, 2017, which is hereby fully incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of making a tobacco extract and to the tobacco extract resulting from that process. The invention also provides cartridges containing the tobacco extract for use in a smoking article, and smoking articles comprising the tobacco extract.

BACKGROUND

Tobacco material is heated in smoking articles for the purpose of releasing substances contained in the material and delivering these as an aerosol.

Smoking articles such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these articles that burn tobacco by creating products that release compounds without burning. Examples of such products are heating devices which release compounds by heating, but not burning, material. The material may be, for example, tobacco or other non-tobacco products, which may or may not contain nicotine.

Electronic cigarettes or “e-cigarettes” are another product that has been formulated as an alternative to combustible products. These devices contain a volatilizable solution which generates an inhalable aerosol on heating. These solutions may contain components of tobacco. It is therefore useful to be able to selectively extract tobacco components.

EP1915064 describes a process for making reconstituted tobacco including a tobacco extraction step. The extraction process uses supercritical carbon dioxide to extract tobacco components, and then contacts the supercritical carbon dioxide containing tobacco components with propylene glycol. The tobacco components transfer into the propylene glycol. The carbon dioxide is supercritical throughout.

SUMMARY

According to a first aspect of the present invention, there is provided a method of making a tobacco extract comprising;

(a) contacting tobacco with an extraction solvent such that tobacco components are extracted from the tobacco into the solvent, wherein the extraction solvent comprises a supercritical fluid;

(b) separating residual tobacco solids from the extraction solvent containing tobacco components;

(c) providing an entrapment solvent in a vessel, exposing the extraction solvent containing tobacco components to conditions in that vessel, wherein the conditions in the vessel are such that the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, and wherein the entrapment solvent dissolves the tobacco components released

from the extraction solvent.

The inventors have established that variations in the extraction process using a supercritical extraction solvent result in variation in the tobacco extract composition and/or in the physical properties of the extract.

Presence of the entrapment solvent results in a tobacco extract that is immediately suitable for use in an electronic cigarette or the like. The transfer to subcritical conditions allows for efficient and effective separation of the tobacco components and extraction solvent. This means that the concentration of tobacco components in the entrapment solvent (i.e. in the tobacco extract) is higher and the chemical make-up is different as compared to the process of EP1915064 (in which the extraction solvent is supercritical throughout). This improves the organoleptic properties of the extract.

The use of subcritical conditions for separation is also advantageous over a process in which the conditions are such that the extraction solvent is supercritical throughout because less energy is required to maintain the conditions. The process is therefore more energy efficient, cheaper to run and is quicker to set up.

In some cases, the entrapment solvent comprises an aerosol generating agent.

In some cases, the entrapment solvent consists essentially or of consists of one or more aerosol generating agents.

In some cases, the extraction solvent used in the above process comprises carbon dioxide. In some cases, the extraction solvent consists essentially of or consists of carbon dioxide.

In some cases, the entrapment solvent used in the above method comprises a polyol. In some cases, the entrapment solvent comprises glycerol and/or propylene glycol.

In some cases, the entrapment solvent consists essentially of or consists of glycerol.

In some cases, the tobacco components extracted by the methods described herein include one or more of nicotine and tobacco aromas and flavors.

In some cases, the method described herein may further comprise the step of providing the entrapment solvent containing dissolved tobacco components (i.e. the tobacco extract) in a cartridge, wherein the cartridge is configured for use in a smoking article.

In some cases, step (a) and step (c) are completed in separate vessels. Step (a) may be completed in a first vessel (or extraction vessel) which is maintained throughout at a temperature and pressure at which the extraction solvent is supercritical. Step (c) may be completed in a second vessel (or separation vessel) which is maintained throughout at a temperature and pressure at which the extraction solvent is subcritical.

In some cases, step (b) includes transfer of the extraction solvent containing tobacco components from the extraction vessel to the separation vessel.

According to a second aspect of the invention, there is provided a tobacco extract obtained by or obtainable by a method described herein.

According to a further aspect, there is provided a cartridge configured for use in a smoking article, the cartridge containing a tobacco extract obtained by or obtainable by a method described herein. The cartridge may be configured for use in an electronic cigarette.

According to a further aspect, there is provided the use of a tobacco extract

obtained by or obtainable by a method described herein to generate an inhalable aerosol. In some cases, the tobacco extract is used in a smoking article to generate the inhalable aerosol.

According to a further aspect, there is provided a smoking article containing a tobacco extract obtained by or obtainable by a method described herein. In some cases, the smoking article may contain the tobacco extract in an insertable cartridge, the cartridge being configured for use in the smoking article. The smoking article may additionally comprise a mouthpiece. The smoking article may additionally comprise a heater which volatilises the entrapment solvent containing tobacco extract in use.

The smoking article may be an electronic cigarette.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only.

DETAILED DESCRIPTION

For the avoidance of doubt, the term “tobacco extract” as used herein refers to the entrapment solvent containing tobacco components.

A supercritical fluid is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. Supercritical fluids can effuse through solids like a gas, and dissolve materials like a liquid. Supercritical fluids have a higher fluid density than gases and therefore have a higher solvent capacity.

In some cases, one or more flavors may be added to the tobacco extract. As used herein, the term “flavor” refers to materials which, where local regulations permit, may be used to create a desired taste or aroma in a product for adult consumers. They may include extracts (e.g., licorice, hydrangea, Japanese white bark magnolia leaf, chamomile, fenugreek, clove, menthol, Japanese mint, aniseed, cinnamon, herb, wintergreen, cherry, berry, peach, apple, Drambuie, bourbon, scotch, whiskey, spearmint, peppermint, lavender, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, honey essence, rose oil, vanilla, lemon oil, orange oil, cassia, caraway, cognac, jasmine, ylang-ylang, sage, fennel, piment, ginger, anise, coriander, coffee, or a mint oil from any species of the genus Mentha), flavor enhancers, bitterness receptor site blockers, sensorial receptor site activators or stimulators, sugars and/or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharine, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanicals, or breath freshening agents. They may be imitation, synthetic or natural ingredients or blends thereof. They may be in any suitable form, for example, oil, liquid, or powder.

As used herein, an “aerosol generating agent” is an agent that promotes the generation of an aerosol on heating. An aerosol generating agent may promote the generation of an aerosol by promoting an initial vaporization and/or the condensation of a gas to an inhalable solid and/or liquid aerosol.

In general, suitable aerosol generating agents include, but are not limited to: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate. In some cases, the aerosol generating agent comprises one or more of glycerol, propylene glycol, triacetin and isopropyl myristate, suitably glycerol and/or propylene glycol.

The weight ratio of aerosol generating agent to tobacco (dry weight) may be from about 2:1 to about 1:3, suitably from 3:2 to about 1:2, suitably about 1:1.

The method according to the invention may additionally comprise an initial step of adding water to the tobacco. The amount of water added may be from about 2% to about 20% based on the dry weight of tobacco, suitably from about 2%, 5% or 8% to 10 about 12%, 15%, 18% or 20%. This pre-treatment with water increases the transfer of polar tobacco components (such as flavors) from the tobacco to the entrapment solvent.

In the process according to the invention, a higher pressure under supercritical conditions increases the solvent capacity and increases the efficiency of extraction. However, more energy is required to achieve and maintain higher pressures. Thus, the supercritical conditions are suitably selected to balance these conflicting requirements. Where the supercritical fluid comprises carbon dioxide, the pressure at which extraction occurs may, in some cases, be from about 8 MPa, 10 MPa, 15 MPa, 20 MPa or 25 MPa to about 85 MPa, 70 MPa, 55 MPa, 40 MPa or 30 MPa, suitably from 8-85 MPa, 15-40 MPa or 20-30 MPa. In some cases, the pressure may be from about 10-16 MPa, suitably about 12 MPa, or may be from about 20-26 MPa, suitably about 23 MPa; the inventors have found that the concentration of TSNAs in the tobacco extract is lower when extraction is completed at these pressures.

Where the supercritical fluid comprises carbon dioxide, the temperature at which extraction occurs may, in some cases, be from about 308K, 318K or 328K to about 473K, 430K, 390K or 350K, suitably from 308-473K, 308-430K, or 328-350K.

The transfer to subcritical conditions reduces the fluid density of the extraction solvent and consequently results in precipitation of the tobacco components. The conditions must be such that the pressure is below the critical pressure of the extraction solvent and/or the temperature is below the critical temperature of the extraction solvent. For thermal efficiency, the conditions are suitably such that the pressure is below the critical pressure of the extraction solvent while the temperature remains above the critical temperature.

The efficiency of separation of the tobacco components and the extraction solvent improves as the conditions move further below the critical point of the extraction solvent. However, the extraction solvent will typically be collected and stored after separation (requiring compression); in some cases, it may be recycled into an extraction chamber. Thus, the subcritical conditions are suitably not too far below the critical point to improve energy efficiency. The subcritical conditions are suitably selected to balance these conflicting requirements. Where the extraction solvent comprises carbon dioxide, the pressure at which extraction occurs may, in some cases, be from about 3 MPa, 4 MPa, 5 MPa or 5.5 MPa to about 7.3 MPa, 7 MPa, 6.5 MPa, 6 MPa, 5.5 MPa or 5 MPa, suitably from 3-7.3 MPa, or 4-6 MPa. Where the extraction solvent comprises carbon dioxide, the temperature of the subcritical conditions under which separation occurs may, in some cases, be from about 280K, 300K, 320K or 330K to about 473K, 430K, 390K or 350K, suitably from 308-473K, 308-430K, or 328-350K.

EXAMPLES

Analytical Methods

Water activity values reported below were measured at 24.9-25.2° C. using the Aqualab Prewater Activity meter. The values were determined using the dewpoint method.

Viscosity values reported below were measured at 25° C. using a Gemini Rheometer from Bohlin Instruments.

Pre-Extraction (Pre-Treatment of Tobacco):

Ground Virginia tobacco leaf of the particle size ranging from 355 μm to 3.5 mm was pre-treated by addition of water (10% of total tobacco weight). The mixture of tobacco and water was left for equilibration for 15 minutes post water addition (which is sufficient time for the water to be fully absorbed).

The pre-treated tobacco (1.2 kg plus 10 wt % water) was placed in a stainless steel extraction basket and the basket placed in an extraction vessel (5 L autoclave). The basket was closed at its ends by sinter metal plates (pore diameter 100 μm, pressure drop across the plate is no more than 1 bar), which distributed the supercritical fluid at the entrance and prevented egress of solid particles at the exit. The use of the basket also allowed the fast charge and discharge of the extraction vessel. The basket was sealed against the extraction vessel wall in order to prevent flow of the supercritical fluid around it.

Example 1 Example of Process According to the Invention

The extraction vessel was linked to a separation vessel by a transfer line. A pressure regulation valve was present in the line. Carbon dioxide may suitably be pumped through the system at the rate 5-23 kg/hr. In this case, carbon dioxide was pumped through the system at the rate of 10 kg/hr. 1.2 kg of glycerol was provided in the separation vessel.

The extraction chamber was maintained at 26 MPa and 338K and the separation chamber was maintained at 4.5 MPa and 318K. Precipitation of the extract in the separation chamber was achieved by pressure and temperature reduction (from supercritical to subcritical conditions), which reduced the fluid density of the carbon dioxide and therefore the solvent-power of the CO₂. The extracted tobacco components were collected in the glycerol at the bottom of the separator.

Gaseous CO₂ exited the separator after passing through a liquid/gas divider (which removed any remaining liquid extract that was entrained in the gas). The CO₂ was collected and recycled into the extraction chamber.

The process was run for three hours and then the CO₂ flow was shut-off. The system was depressurized (to atmospheric conditions). The glycerol containing tobacco components was then drained from the separator vessel and weighed.

Comparative Test

A comparative test was run using the same apparatus as in example 1. However, the conditions were supercritical (26 MPa and 338K) throughout the apparatus. All other aspects of the comparative test were the same as in example 1.

The comparative test is a representative example of the processes described generally in EP1915064.

Data

Tobacco Extract Properties:

Nicotine Water NNN NNK Viscosity Density Water activity Experiment (mg/g) (wt %) (ng/g) (ng/g) (Pa s) pH (g/cm³) (Aw) Example 1* 7-11 7.5-9 120-170 70-85 0.23 7.9 1.24 0.25-0.3 Comp. test 4.7 5.5 71.1 49.1 0.32 6.73 1.25 0.24 *The process of example 1 was run 6 times. Where ranges are provided in the data table, all examples are encompassed in that range. Where a single value is provided, the value is the mean value.

It can be seen that the pH of the extracts obtained in example 1 is higher than the extract resulting from the comparative test. This increases the availability of nicotine in the solution when used in an electronic cigarette.

Similar results have been observed when using Oriental or Burley starting tobaccos.

The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive.

It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future. 

1. A method of making a tobacco extract, the method comprising: (a) contacting tobacco with an extraction solvent such that tobacco components are extracted from the tobacco into the solvent, wherein the extraction solvent comprises a supercritical fluid; (b) separating residual tobacco solids from the extraction solvent containing tobacco components; (c) providing an entrapment solvent in a vessel, exposing the extraction solvent containing tobacco components to conditions in that vessel, wherein the conditions in the vessel are such that the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, and wherein the entrapment solvent dissolves the tobacco components released from the extraction solvent.
 2. The method according to claim 1, wherein the extraction solvent comprises carbon dioxide.
 3. The method according to claim 2 wherein at (a), the temperature is in the range of about 308-473K, preferably about 328-350K, and the pressure is in the range of about 8-85 MPa, preferably about 20-30 MPa.
 4. The method according to claim 1, wherein the entrapment solvent comprises an aerosol generating agent.
 5. The method according to claim 4, wherein the entrapment solvent comprises a polyol such as glycerol and/or propylene glycol.
 6. The method according to claim 1, wherein the tobacco components include one or more of nicotine and tobacco aromas and flavors.
 7. The method according to claim 1, further comprising providing the entrapment solvent containing dissolved tobacco components in a cartridge, wherein the cartridge is configured for use in a smoking article.
 8. A tobacco extract obtainable by a method according to claim
 1. 9. A cartridge configured for use in a smoking article, the cartridge containing a tobacco extract according to claim
 8. 10. A smoking article containing a tobacco extract according to claim
 8. 11. Use of a tobacco extract obtainable by a method according to claim 1 to generate an inhalable aerosol.
 12. Use of a tobacco extract according to claim 11, wherein the tobacco extract is used in a smoking article. 